Frithjof R. von der Fehr

Experimental Caries in Man

The purpose of the present study was to develop a method for short-term caries trials in man, using an experimental model already employed in periodontal research. Twelve students were given prophylaxis and instruction to practice meticulous oral hygiene until Plaque Index and Gingival Index approached zero. The carious state of the bucco-gingival enamel areas, excluding molars, was evaluated using a dissection microscope. The cleaned and dried tooth surfaces were scored according to the Caries Index system. During a period of 23 days without oral hygiene 6 participants performed 9 daily mouthrinses with 10 ml of a 50% sucrose solution. At the termination of this period the sucrose group demonstrated a higher mean Caries Index and a greater number of new early lesions than the six control subjects. The mean Plaque Index scores were higher in the sucrose group, whereas the Gingival Index scores were similar for both groups. Smears of plaque showed no significant differences in the percentage distribution of various types of microorganisms. After 30 days of oral hygiene and daily mouthrinses with 0.2 % NaF, fair agreement was found between the Caries Index scores of the two groups. Similar observations were made after a second hygiene and fluoride period. The results demonstrate that it is possible to produce detectable carious alterations within 23 days by abolishment of oral hygiene and frequent sucrose additions and that these alterations are reversible.

Oral hygiene and caries: A review

On the basis of existing literature, efficient oral hygiene was found to have a caries preventive effect. The quality of the cleaning appears to be more important than the frequency of its performance. Professional tooth cleaning at regular intervals may inhibit caries on all tooth surfaces. The effect of self-performed oral hygiene has been demonstrated mainly on free smooth surfaces and on front teeth.

Analyses of the caries decline and incidence among Norwegian adolescents 1985-2000.

Since most studies of caries decline are descriptive time-trend analyses, the purpose of this article was to identify factors statistically associated with the caries decline among Norwegian adolescents after 1985. The DMFT scores for the age groups 12 and 18 years reported annually by 19 counties were analysed. The average caries-free proportions of 18-year-olds increased from 2% to 15% between 1985 and 2000, while the DMFT declined by 49%; 10.2 - 0.75 to 5.2 - 0.78. The decline for the 12-year-olds was 53%. The mean DT at the dentinal level remained at about 0.8 for 12-year-olds and 1.5 for 18-year-olds throughout the observation period. There was no significant difference in DMFT increment from age 12 to 18 between the birth cohorts 1973 (3.8 - 0.46) and 1982 (3.0 - 0.52) when controlling for counties. The variables migration and children per dentist were significantly associated with the DMFT decline in multivariate analyses. The caries decline for 18-year-olds was significantly steeper before than after 1990. The decline among the 18-year-olds may be attributed to fluoride and more restrictive criteria for placement of fillings in teenagers in the 1980s and fewer filled teeth before the age of 12 years in the 1990s.

Fluoride release and uptake in vitro from a composite resin and two orthodontic adhesives

The aim of this study was to investigate the fluoride release and uptake characteristics of a composite resin (Tetric) and two orthodontic adhesives (VP 862 and Saga Bond), with a type-II glass ionomer cement (Ketac Fil) as a control. Test specimens in 2 ml deionized water released fluoride over a period of 33 days. Ketac Fil released 54 and 15 times more fluoride than Tetric after 24 h and 1 month, respectively, whereas the two adhesives released amounts between these values. Specimen exposure to 1000-ppm NaF solution increased the 24-h fluoride release from all materials, with near pre-exposure levels reached after 2-3 days. Ketac Fil had a tendency to recharge not seen with the other materials. The ytterbium trifluoride filler in Tetric has a very low water solubility, and it is therefore suggested that the increases in fluoride release from Tetric after exposure to fluoride were most probably due to release of surface-retained fluoride.

Saucer-shaped cavity preparation for composite resin restorations in class II carious lesions: Three-year results

This study determined the feasibility of saucer-shaped cavity preparations for composite resins in class II lesions. Saucer-shaped class II cavity preparations were restored with composite resin and subjected to clinical, radiographic, and replica cast evaluation (39 restorations) after 6, 18, and 36 months. The results indicated that the retention, resistance form, and wear resistance of the class II saucer-shaped cavity preparations were satisfactory after 3 years.

Changes in plaque fluoride levels by school-based fluoride rinsing and tablet programs in Bangladesh

The aim of this study was to evaluate the effects of school-based fluoride rinsing and tablet programs on plaque fluoride levels. A total of 42 children (8-9 years) were selected from two neighboring schools in Dhaka, Bangladesh. After caries recordings, vestibular plaque samples from the maxillary central incisors and mandibular first molars were collected and frozen on day 0 (baseline). The subjects of one school (rinsing group, n = 15) rinsed with 0.05% NaF, while those from the other school (tablet group, n = 16) used a 0.5 mg F tablet on the 5 school days during a 3-week period. The surfaces were sampled on the first and last school day every week. The fluoride and protein contents of each sample were analyzed using micro-techniques. The median plaque fluoride levels were 9.1 ppm at baseline in the rinsing group and 2.5 ppm in the tablet group (P < 0.05). This difference could in part be related to reported fluoride toothpaste usage. After 4 days on the fluoride programs, plaque fluoride levels in the rinsing group increased to 27.3, 24.5 and 14.2 ppm in the 3 consecutive weeks. The corresponding values after tablet usage were 8.0, 6.5 and 7.1 ppm, respectively. After 3 days without fluoride during the weekends, levels declined towards baseline values in both groups. Hence, the plaque fluoride levels in 8 to 9-year-old Bangladeshi children were increased by both rinsing and tablet programs, but the effect was not detectable 3 days later.

Evaluation for Improvement ‐a Case Study

Abstract: Lauvas, P., Skogedal, O. & von der Fehr, F. R. 1980. Scandinavian Journal of Educational Research 24,61‐78. The present paper is a micro‐level study of one lecture within dental education directed at 3 problems, all related to the problems of having ones own teaching evaluated and improved. The results suggest that some cautiousness should be placed on interpreting student ratings of teaching to indicate teaching effects on student learning. Student ratings are valuable feedback on the presentation made by the teacher but do not always correspond to learning results.